In particular instances mating electrical connectors are brought into mated engagement remote from the ability of a person to manipulate them into proper axial and angular alignment necessary for their corresponding terminals to properly engage and mate in associated pairs. For these connectors their movement together is mechanically constrained and is based on being guided by means on the framework to which they are mounted into approximately the proper axial and angular alignment relative to each other. However, especially on high density connectors having many small terminals, precise alignment is necessary which cannot be practically provided by the framework guiding means, so the connectors must include integral alignment mechanisms which complete the alignment prior to the mating engagement of the terminals. Such precise alignment also assures that the keying mechanisms operate appropriately, to allow keying of connectors intended to mate, and disallow mating of connectors not intended to mate.
Conventional alignment mechanisms include a spaced pair of sturdy elongated alignment posts of substantial diameter extending forwardly from one connector received into corresponding holes of the other connector. Such connectors include rack and panel connectors where one of the connectors is float mounted on its framework and thus is capable of incremental lateral movement, such as are sold by AMP Incorporated, Harrisburg, Pennsylvania under the trade designation METRIMATE Drawer Connector and also connectors such as are disclosed in U. S. Pat. No. 4,664,456. Tapered frustoconical bearing surfaces at the leading ends of the alignment posts engage corresponding tapered frustoconical bearing surfaces comprising entrances to the corresponding holes when the connectors near each other, because the connectors are commonly slightly misaligned both axially and angularly. Upon engagement of the bearing surfaces, the connector permitted to incrementally adjust will move and align itself with the fixed other connector as the alignment posts enter fully into the corresponding holes, the alignment posts being long enough to effect axial alignment of the connectors prior to mating engagement of the contact terminals.
Certain rack and panel connectors are known which are provided with metal plating on the posts and on the wall surfaces of the corresponding holes, the metal plating being conductively connected to chassis ground, which serves to enable discharge of any electrostatic potential (ESD) existing between the connectors prior to the mating of the contact terminals. Theoretically, if the connectors were approaching each other in precise alignment the bearing surfaces of the alignment posts and the corresponding posts would not engage. Thus if the bearing surfaces of the posts and holes were conductive, but no engagement occurred, no discharge would occur of the electrostatic potential to ground prior to engagement of the contact terminals. Although unlikely, that possibility is substantial enough so that ESD protection is not considered assured. In addition, there is a more probable situation wherein the connectors are almost aligned in which case the bearing surfaces would engage only in the latest stages of alignment post entry; it is possible that discharge could occur elsewhere in the connector by nearly touching conductive elements.
It is desirable to obtain a mating pair of connectors which align themselves during a remote or mechanically constrained axial mating procedure and which provide for assured protection against electrostatic potential influence on the electrical connections being established between the connectors and the systems being connected.
Electrical connectors are known for the transmission of electrical signals which must be protected from electromagnetic and radio frequency interference (EMI/RFI), by providing conductive shielding completely around the connectors in their mated state, with the shielding being electrically connected to a conductive grounding shield of the electrical cables as if it were a continuous extension thereof. The conductive shielding of the connectors is most commonly in the form of metal shells within which are inserts of dielectric material housing the terminals terminated to the respective conductor wires of the cables; conductive shielding can also take the form of metallized plating on plastic connector housings. When the connectors are in their mated state there must be no axial gap between the shells laterally of the terminals therewithin, and there must be an electrical connection between the shells of the mating connectors upon mating, preferably a plurality of such connections surrounding the housings therewithin. The conductive shells of the respective connectors enter into grounding engagement with each other prior to terminal mating.
Such a system of EMI/RFI protected connectors is disclosed in U.S. Pat. No. 4,808,115 for a "Line Replaceable Connector Assembly for use with Printed Circuit Boards", wherein the dielectric housing containing the terminals of the LRM connector precisely aligns itself with the mother board connector by incrementally moving itself laterally within its shell in response to a forwardly extending alignment rib entering into a recess of the mother board connector. The disclosed grounding engagement between the respective shells is relatively independent of precise alignment of the connectors. The LRM shell is secured to cover plates of the LRM which are fastened to a central cool plate having a pair of flanges extending outwardly from opposing sides of the LRM which move along and are constrained by opposed LRM-guiding channels along side walls of the enclosure of the control unit extending outwardly from the mother board connector and approximately aligned therewith. The forward end of the LRM shell is laterally spaced from the connector housing and receives the forward end of the mother board connector shell thereinto. The forward end of the LRM shell includes mounted peripherally around its inner surface a continuous strip of EMI spring fingers extending inwardly and rearwardly which engage the mother board connector shell's forward end; the spring fingers being resilient can forgive the shells being only approximately instead of precisely aligned with each other while establishing an assured grounding engagement between the shells peripherally around the housings. After insertion, alignment and mating, conventional wedging lock mechanisms may be used which are adjusted to wedge and lock the LRM in place within the opposing channels. The mother board connector shell is rigidly mounted to the framework of the control unit and is electrically connected to chassis ground.
It is also desirable to provide a system of matable connectors which align themselves during mating, and which are protected against EMI/RFI as well as against ESD.
It is further desirable that the system of aligning the connector housings also maintain a metal shell of the fixedly mounted connector housing in precisely located relationship with its housing to enable keying elements secured to the metal shell to be aligned with cooperating keying elements of the mating movable connector.